JPH11135128A - Electrode for alkaline secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize a current distribution in an electrode due to rapid charging and discharging and maintain high capacity over long period by having a conductive agent powder and an active substance, in which a skin membrane consisting essentially of silver and/or copper is adhered to at least a part of its surface. SOLUTION: As a skin membrane consisting essentially of silver or copper or both, in practice a silver alloy membrane, a silver/copper double membrane, a silver/copper alloy double membrane, a nickel/silver double membrane, and a nickel/copper double membrane are preferred. As a silver alloy, copper cobalt, and nickel alloy is exemplified, and a copper alloy, a copper, nickel, lead, and tin alloy is exemplified. A conductive agent powder for adhering this skin membrane preferably includes nickel powder, carbon powder, or carbon/nickel powder. To make the skin membrane adhere, for example, a method for soaking the conductive agent powder in a plating bath containing silver ion or copper ion, thereby performing electrolytic or electroless plating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for an alkaline secondary battery, and more particularly to a conductive agent powder having a silver or copper film or both of them coated on at least a part of its surface. And a hydrogen storage alloy electrode (negative electrode) for an alkaline secondary battery having a substance.

[0002]

2. Description of the Related Art Conventionally, as a secondary electrode for an alkaline secondary battery, a positive electrode using nickel hydroxide as an active material and a negative electrode using a hydrogen storage alloy as an active material, a so-called hydrogen storage alloy electrode, have been known. Each of these electrodes is formed into a desired shape by various methods by blending various conductive agents with the active material powder.

Japanese Patent Application Laid-Open No. Hei 2-201870 discloses a technique for forming a porous metal layer by plating nickel or copper on the surface of a hydrogen storage alloy powder. It is said that a hydrogen storage alloy electrode containing as a main component is excellent in moldability, oxidation resistance, utilization factor, and the like. Japanese Patent Application Laid-Open No. 7-85866 discloses a method in which cobalt powder or hydrogen storage alloy powder is dispersed on the surface of hydrogen storage alloy powder and plated with nickel, and a hydrogen storage alloy electrode having the powder is immersed in a high-temperature alkali. Disclosed are techniques for processing, in which high activity, high capacity and long life are obtained.

Japanese Patent Publication No. 50607/1995 discloses a hydrogen storage electrode for an alkaline storage battery in which a hydrogen storage material is mixed with a carbonyl nickel powder having a three-dimensional chain structure and a diameter of 1 μm or less as a conductive material. The patent discloses that high energy and long cycle life characteristics can be obtained.

In an electrode of an alkaline secondary battery, gas occlusion / release and liquid permeation / emission are repeated in the electrode during charging / discharging, so that fine particles of a filler such as an active material and a conductive agent are advanced. The finely divided filler is liable to fall off the electrode. In particular, in the case where the current distribution of the electrodes is non-uniform, the falling-off phenomenon of the filler tends to occur at a place where a large current flows.

At present, nickel-plated mild steel used for a current collector substrate of a current collector has high conductor resistance and low conductivity.
Also, nickel hydroxide used as a positive electrode active material,
Hydrogen storage alloy used for the negative electrode, nickel powder, carbon powder or carbonyl nickel powder blended as a conductive agent with these, cobalt powder added to form a conductive matrix of cobalt oxyhydroxide in the positive electrode, oxidation Cobalt compounds such as cobalt and cobalt hydroxide also have relatively high electrical resistance and are likely to cause uneven current distribution. As a result, a portion where the current is concentrated in the electrode is generated particularly by repeating the rapid charging and discharging, and the falling off of the filling material easily occurs. The detachment of the filler is a factor for short-circuiting between the positive and negative electrodes and losing the function as an electrode, and significantly reduces the battery life. In the electrode obtained by plating nickel or copper on the above-mentioned hydrogen storage alloy, it is assumed that the uniformity of the current distribution can be solved to some extent.However, nickel has low conductivity, and copper is relatively oxidized by the battery reaction. Further improvement is required because it is easy. Further, when the above metal is plated on the hydrogen storage alloy, the original function of the hydrogen metal alloy may possibly be hindered, depending on the thickness of the coating.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode for an alkaline secondary battery capable of maintaining a high capacity over a long charge / discharge cycle by making the current distribution in the electrode uniform with rapid charge / discharge. Aim.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and as a result, at least a part of the surface is essentially coated with silver or copper or a film of both of them as a conductive agent. The present inventors have found that a high capacity can be maintained over a long charge / discharge cycle by blending an electrode with a conductive agent powder whose surface electric resistance has been lowered by being attached, and completed the present invention.

According to the present invention, there is provided an alkaline secondary battery comprising an active material and a conductive agent powder having a coating essentially consisting of silver, copper, or both on at least a portion of its surface. Electrode. Specifically, a silver-only film,
A positive electrode for an alkaline secondary battery having a silver alloy single film, a silver / copper double film, or a conductive agent powder coated with a silver / copper alloy double film and γ-nickel oxyhydroxide as an active material. Also, a conductive agent powder coated with a silver-only film, a copper-only film, a silver / copper double film or a nickel / copper double film, preferably a carbonyl nickel powder having a three-dimensional chain structure and a hydrogen storage alloy powder A hydrogen storage alloy electrode (negative electrode) having

In another aspect of the present invention, a conductive agent powder is immersed in an electrode material in a plating bath having essentially silver ions or copper ions, and the electrode material is essentially made of silver under electroplating or electroless plating conditions. , Copper, or a mixture of both, is deposited, and a conductive agent powder applied to at least a part of the surface of the conductive agent powder is blended and formed into a predetermined shape. This is a method for manufacturing a battery electrode.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The electrode for an alkaline secondary battery of the present invention comprises a conductive agent powder coated with a film consisting essentially of silver, copper or both, and a γ-nickel oxyhydroxide powder as an active material. Or a hydrogen storage alloy electrode (negative electrode) having a hydrogen storage alloy powder.

The electrical resistance of silver and copper is 1.47 ρ / Ω · m and 1.55 ρ / Ω · m at 0 ° C., which is higher than that of nickel generally used for current collector plating and conductive agent powder. 6.2 ρ / Ω · m and 5.6 ρ / Ω · of cobalt
m, the presence of a conductive agent powder coated with a film consisting essentially of silver, copper, or both, having a low electric resistance in the electrode, results in a current in the electrode. Not only the loss is reduced, but also the current distribution in the electrode is made uniform.

In the present invention, the film consisting essentially of silver, copper or both is a silver-only film, a silver alloy-only film,
A copper single film, a silver / copper double film, a silver / copper alloy double film, a nickel / silver double film, a nickel / copper double film, and the like. From the viewpoint of electric resistance, a silver single film or a copper single film is preferable. However, silver is expensive and copper is easily oxidized. Therefore, practically, silver alloy film, silver / copper double film, silver / copper alloy double film, nickel / silver double film, nickel / copper Multilayers are preferred. In the case of a silver film or a silver alloy film, the thickness of the film is 0.5 μm or less, preferably 0.01 to 0.3 μm, and a copper film, a copper alloy,
In the case of a nickel film, it is approximately 1 μm. These films function sufficiently if they are applied only to at least a part of the surface of the conductive agent powder, but most preferably cover the entire surface of the conductive agent powder.

The silver alloy is represented by the formula: Ag · X, wherein X is copper, cobalt, nickel, phosphorus, antimony, selenium, palladium, etc. Although they do not have to be in a solid solution, their content is 0.1% by weight or less, preferably 0.05% by weight.
Hereinafter, it is most preferably 0.02 to 0.01% by weight. Examples of the copper alloy include a compound represented by the formula: Cu · Y, wherein Y is a compound such as nickel, lead, tin, or zinc. The Y component may or may not be dissolved. However, their content may be 0.1% by weight or less, preferably 0.05% by weight or less, most preferably 0.02 to 0.02% by weight.
1% by weight.

In the present invention, the conductive agent powder to be coated with the film is a general conductive agent powder blended in an electrode for an alkaline secondary battery, for example, a metal powder such as cobalt or nickel, carbonyl nickel, carbon And conductive inorganic powders. The preferred conductive agent powder is a nickel powder, a carbon powder or a carbonyl nickel powder. In the case of a hydrogen storage alloy electrode, a carbonyl nickel powder having a three-dimensional chain structure is particularly preferable.

In the present invention, the coating consisting essentially of silver, copper, or both is formed by electroplating, electroless plating, or CVD (Chemical Vapor Depo).
position), PVD (Physical Vapo)
r Deposition) can be applied to at least a part of the surface of the conductive agent powder. In particular, electroplating and electroless plating, which can easily cover the entire surface of the conductive agent powder, are preferably employed. That is, the conductive agent powder is immersed in a plating bath containing silver ions or copper ions, and a film consisting essentially of silver, copper, or both is formed on the surface of the conductive agent powder under electrolytic or electroless plating conditions. At least partially adhere. The conductive agent powder is
Prior to the plating treatment, it is preferable to perform a surface roughening treatment using a high-temperature alkaline aqueous solution, for example, sodium hydroxide, potassium hydroxide, lithium hydroxide or the like in advance.

The following are examples of the plating bath composition used for plating the conductive agent powder. a) Silver single plating and silver compound plating a-1) Electroless silver bath-1: NaAg (CN) ₂ : 0.01 mol / l, NaCN:
0.2 mol / l, NaOH: 0.4 mol / l, KB
_{H 4: 0.01mol / l a-} 2) an electroless silver bath _{-2: NaAg (CN) 2:} 0.05mol / l, NaCN:
0.1 mol / l, NaOH: 0.4 mol / l, KB
H ₄ : 0.01 mol / l a-3) Silver cyanide bath: AgCN: 5 g / l, KCN: 60 g / l, K ₂ C
O ₃ : 15 g / l a-4) Silver sulfate bath: Ag ₂ SO ₄ : 40 g / l, KI: 200 g / l, NH
₄ OH: 30 g / l, Na ₄ P ₂ O ₇ : 25 g / l a-5) Silver-antimony bath: KAg (CN) ₂ : 55 g / l, potassium antimonate tartrate · 0.5H ₂ O: 1 g / l, KCN: 40 g / l,
_{K 2 CO 3: 15g / l} , NaOH: 10g / l a-6) silver - indium _{bath: KAg (CN) 2: 55g} / l, KIn (CN) 2: 1
g / l, KCN: 40 g / l, K ₂ CO ₃ : 15 g /
l, NaOH: 10g / l a -7) silver - cobalt _{bath: KAg (CN) 2: 55g} / l, CoSO 4 · 7H
₂ O: 1 g / l, citric acid: 40 g / l, sodium citrate: 40 g / l a-8) silver-selenium bath: a-9) silver-copper bath: KAg (CN) ₂ : 55 g / l, KCu (CN) ₂ : 1
g / l, KCN: 40 g / l, K ₂ CO ₃ : 15 g /
1, NaOH: 10 g / l a-10) Silver-nickel bath: AgCl ₂ : 20 g / l, NiCl ₂ .6H ₂ O: 1 g
_{/ L, Na 2 S 2 O} 3: 100g / l a-11) Silver - palladium _{bath: KAg (CN) 2: 20g} / l, PdCl 2 · 4H
₂ O: 1 g / l, KCN: 40 g / l, K ₂ CO ₃ : 1
5 g / l, NaOH: 10 g / l

[0018] b) Copper plating and copper compounds plating b-1) an electroless copper baths _{-1: CuSO 4 · 5H 2 O} : 0.03mol / l, EDTA
4Na: 0.04 mol / l, NaOH: 0.10 m
ol / l, formaldehyde: 0.23 mol / l, additive 2,9-dimethyl-1,10-phenanthroline:
80mg / l b-2) an electroless copper baths _{-2: CuSO 4 · 5H 2 O} : 15g / l, EDTA · 2N
a: 45 g / l, paraformaldehyde: 15 g / l,
Additives α, α'-dipyridyl: 10 mg / l, potassium nickel cyanide: 15 mg / l b-3) Copper cyanide bath: CuCN: 70 g / l, NaCN: 80 g / l, free N
aCN 8 g / l, NaOH: 20 g / l b-4) Copper-zinc bath: KCu (CN) ₂ : 60 g / l, K ₂ Zn (CN) ₄ :
1 g / l, KCN: 20 g / l, Na ₂ SO ₄ : 15 g
/ L b-5) Copper-tin bath: KCu (CN) ₂ : 80 g / l, NaSnO ₃ .H
₂ O: 1 g / l, KCN: 25 g / l, NaOH: 10
g / l b-6) Copper-lead bath KCu (CN) ₂ : 50 g / l, Pb (CH ₃ COO)
₂ Pb (OH) ₂ : 1 g / l, KCN: 20 g / l, potassium sodium tartrate · 0.5H ₂ O: 30 g / l,
KOH: 2g / l b-7 ) Copper - Nickel _{bath: CuSO 4 · 5H 2 O:} 50g / l, NiSO 4 · 7H
_{2 O: 1g / l, K} 2 P 2 O 7 · 3H 2 O: 200g /
1, butynediol (40%): 1 g / l c) nickel plating c-1) nickel sulfamate bath: nickel sulfamate: 350 g / l, boric acid 30 g
/ L, nickel chloride: 25 g / l

Examples of the electroplating method include a method of arranging a silver plate or a copper plate as a positive electrode on both sides of a negative electrode covered with a hydrogen storage alloy powder with a diaphragm, and a method of using an internal anode type rotary inclined barrel plating apparatus. Can be adopted. The thickness of the film can be adjusted by selecting plating conditions such as plating time for electroless plating, and current density and plating time for electrolytic plating.

In the present invention, the electrode material is mixed with a conductive agent powder coated with a film consisting essentially of silver, copper, or both, and formed into a predetermined shape by a conventional method. To manufacture. Examples of the electrode material to be mixed with the electrode in addition to the conductive agent powder include an active material powder and a binder for a positive electrode, and an active material powder and a binder for a negative electrode.

The active material incorporated in the positive electrode is usually nickel hydroxide, in which zinc and / or a compound thereof and cobalt and / or a compound thereof are dissolved in solid form or are simply mixed. May exist. In a positive electrode according to a preferred embodiment of the present invention, the active material is γ-nickel oxyhydroxide, and zinc and / or a compound thereof, and cobalt and / or a compound thereof are dissolved in or mixed therewith. May be present. γ-nickel oxyhydroxide is an oxidized form of nickel hydroxide, and can be obtained by a method of electrolytic oxidation using nickel hydroxide as an anode or a method of chemical oxidation using an oxidizing agent. Preferred active materials have a particle size of 1-2.
00 μm, preferably 10-60 μm spherical, hemispherical,
Or a chicken egg-like powder.

In the present invention, the active material blended in the negative electrode is a hydrogen storage alloy. MmN as a hydrogen storage alloy
i ₅ (Mm is a misch metal) type, LaNi ₅ type (for example, La _0.7 Nd _0.2 Ti _0.1 Ni _2.5 Co _2.4 Al
_0.1 ), TiNi-based (for example, Ti _0.5 Zr _0.5 Ni
_1.0 ), ZrNi ₂ .ZrV ₂ system (for example, ZrMn
_{0.6 Cr 0.2 Ni 1.2 · Ti 17} Zr 16 V 22 Ni 39 C
r ₇ ) are currently known, any of which can be used. Hydrogen storage alloy is usually 100 μm
Hereinafter, it is preferably blended with the electrode as a fine powder mechanically pulverized to about 50 to 70 μm.

[0023]

The present invention will now be described more specifically with reference to examples. (1) having γ-nickel oxyhydroxide as an active material
Positive electrode example 1 1) Silver plating of nickel powder Nickel powder was immersed in an aqueous solution of potassium hydroxide (concentration: 30 g / l) at a temperature of 80 ° C for 30 minutes to perform a surface roughening treatment, and then the above electroless silver bath was used. -1: a-1) for 3 seconds to obtain a nickel powder: Ag // Ni whose surface was entirely covered with a silver-only film having an average plating thickness of 0.05 μm.

2) Positive Electrode With respect to 100 parts by weight of γ-nickel oxyhydroxide in which 5% by weight of spherical zinc having a particle size of 1 to 200 μm is dissolved,
A paste obtained by blending and mixing 10 parts by weight of the nickel powder coated with the silver-only film prepared above, 2 parts by weight of cobalt oxide (CoO) powder, and 2 parts by weight of PTFE as a binder is foamed with a porosity of 95% by volume. It was filled in an electrode substrate made of a nickel porous body and dried and pressed. The obtained electrode substrate was immersed in a suspension containing 1% by weight of PTFE, dried again, and then pressed with a roll press to produce a 0.7 mm-thick sheet-like electrode, which was used as a positive electrode.

3) Negative electrode Hydrogen storage alloy (MmNi _3.2 Co _1.0 Al _0.2 M
n _0.4 : Mm is a misch metal) mechanically pulverized, 100 parts by weight of fine powder having an average particle size of 65 μm, 10 parts by weight of untreated nickel powder and PTF as a binder.
A paste prepared by mixing E2 parts by weight and 1 part by weight of CMC and uniformly mixing was applied to a punched nickel sheet of a mild steel sheet nickel-plated to a thickness of 3 μm, dried and rolled to produce a hydrogen storage alloy electrode, This was used as a negative electrode.

4) Separator A polyolefin-based nonwoven fabric (trade name: FT-310, manufactured by Japan Vilene Co., Ltd.) is washed with water to remove the attached nonionic surfactant, dried, and then dried at a temperature of 100 ° C. and a concentration of 9%.
It was immersed in 5% concentrated sulfuric acid for 30 minutes. Next, the nonwoven fabric was sufficiently washed with running water, dried at a temperature of 80 ° C. for 1 hour, immersed in a 1% sodium hydroxide aqueous solution for 5 minutes, and further washed with water. Separately prepared polyamide-based nonwoven fabric [trade name: FT-773, Nippon Vilene Co., Ltd.] washed with water, dried, both surfaces thereof combined scissors above pretreated polyolefin nonwoven, under pressure 3 kg / m ² Temperature The resultant was dried at 80 ° C. and integrated to prepare a 1: 1 polyolefin-based nonwoven fabric: polyamide-based nonwoven fabric separator.

5) Battery assembly and 500 cycle life test NaOH: 0.6 N, LiOH: 1 N, KOH: 7 N as the positive electrode, negative electrode, separator and electrolyte prepared above.
Nominal capacity of 1,400m using alkaline electrolyte
An Ah AA size nickel-metal hydride battery was assembled and left at room temperature for 16 hours. Next, charging was performed at 0.2 C for 1.5 hours and discharging at 0.2 C to a battery voltage of 1 V was repeated three cycles to perform initial activation. Next, the assembled battery was charged at 1,400 mA for 1.5 hours at 20 ° C. ± 2 ° C., left for 1 hour, discharged at 1,400 mA until the discharge end voltage reached a discharge state of 1 V, and stopped 0.5. A cycle life test in which the time was one cycle was performed. 50
Table 1 shows the discharge capacity retention rate after 0 cycles.

Example 2 The same nickel powder as used in 1) of Example 1 was used.
It was immersed in the above-mentioned electroless copper bath-1 at 70 ° C .: b-1) for 5 minutes to obtain a nickel powder: Cu // Ni coated with a copper single film having an average thickness of 1 μm. Next, the nickel powder coated with the obtained copper film was immersed in the same electroless silver bath-1: a-1) as in 1) of Example 1, and the average thickness was 0.05 μm.
A silver film having a thickness of m / m was formed on the copper film, and a nickel powder: Ag / Cu // Ni having a silver / copper double film adhered thereon was obtained.

Except for using the obtained nickel powder coated with the silver / copper double film, a positive electrode was prepared in the same manner as in 2) of Example 1 to prepare a positive electrode. A nickel-metal hydride battery was manufactured by combining the separator of 4) and the alkaline electrolyte of 5), and a 500 cycle life test was performed under the same conditions as in 5) of Example 1). Table 1 shows the test results.

Examples 3 to 9 In Example 1) 1), the plating bath was the silver alloy bath described above: a-5) to a-11), and the hydrogen-absorbing alloy powder was covered with a diaphragm to form a negative electrode. A silver plate is placed as a positive electrode and electroplating is performed, silver-antimony (0.01% by weight), silver-indium (0.01% by weight), silver-cobalt (0.02% by weight), silver-selenium (0.01% by weight), silver-copper (0.01% by weight), silver-nickel (0.
02% by weight) and silver-palladium (0.02% by weight)
Powder coated with a silver alloy single film: Ag · Sb /
/ Ni, Ag-In // Ni, Ag-Co // Ni, A
g.Se//Ni, Ag.Cu//Ni, Ag.Ni/
/ Ni and Ag.Pd // Ni were obtained. Hereinafter, a positive electrode was prepared in the same manner as in 2) of Example 1 by using the obtained nickel powder coated with the silver alloy single film, and a battery was assembled using the positive electrode under the same conditions as in Example 1. A cycle life test was performed. Table 1 shows the test results.

Examples 10 to 13 In Example 2, the above-mentioned copper alloy baths: b-4) to b-7) were used in place of the electroless copper bath-2.
The positive electrode of the electroplating apparatus used in step 1 was replaced with a copper plate, and a copper alloy film was applied to nickel powder. The same treatment as in Example 2 was performed to obtain silver / copper-zinc (0.01% by weight) and silver / copper. Tin (0.01% by weight), silver / copper-lead (0.01% by weight),
Nickel powder coated with silver / copper-nickel (0.01% by weight) silver / copper compound double film: Ag / Cu.Zn //
Ni, Ag / Cu.Sn // Ni, Ag / Cu.Pb /
/ Ni and Ag / Cu.Ni // Ni were obtained. Less than,
A positive electrode was prepared in the same manner as in Example 1, and a battery was assembled using the positive electrode. A 500 cycle life test was performed under the same conditions. Table 1 shows the test results.

Comparative Example 1 A positive electrode was prepared in the same manner as in Example 1 except that untreated nickel powder was used as the conductive agent in 2) of Example 1, and a battery was assembled using the positive electrode. 5 by condition
A 00 cycle life test was performed. Table 1 shows test results
Shown in

[0033]

[Table 1]

(2) Negative electrode having hydrogen storage alloy powder (water
Nitrogen storage alloy electrode) Example 14 1) Silver plating of nickel powder Nickel powder was immersed in an aqueous potassium hydroxide solution (concentration: 30 g / l) at a temperature of 80 ° C for 30 minutes to perform surface roughening treatment. Silver plating was carried out using the internal anode type rotating inclined barrel plating apparatus shown in FIG. 1 and the silver cyanide bath: a-3) under the conditions of an average current density of about 0.2 A / dm ² and a plating time of about 4 minutes. Perform, average thickness is about 0.5μ
Nickel powder coated almost entirely with a silver-only film of
Ag // Ni was obtained.

2) Positive electrode In 2) of Example 1, the active material was changed to a particle size of 1 to 200 μm.
A positive electrode was produced in the same manner as above except that nickel hydroxide in which 5% by weight of spherical zinc was dissolved was used and the conductive agent was replaced with untreated nickel powder.

3) Hydrogen storage alloy electrode (negative electrode) In 3) of Example 1, nickel powder coated almost entirely with the silver-only film obtained above was used instead of nickel powder mixed in the negative electrode. A hydrogen storage alloy electrode was prepared in the same manner as in Example 1, 3) except that the hydrogen storage alloy electrode was used.

4) Battery assembly and 1,000 cycle life test The above-prepared positive electrode, hydrogen-absorbing alloy electrode (negative electrode), a separator produced by the same treatment as in 4) of Example 1, and the same specifications as Example 1 AA-size nickel-metal hydride battery having a nominal capacity of 1,200 mAh was assembled using the alkaline electrolyte of the above. The assembled battery was subjected to a cycle life test in which the battery was charged at 0.5 C for 3 hours, left for 1 hour, discharged at 0.5 C until the discharge end voltage reached a discharge state of 1 V, and 0.5 cycle of rest as one cycle. Was. 1,0
Table 2 shows the discharge capacity retention ratio after the lapse of 00 cycles. In addition, the internal resistance in Table 2 was measured at an alternating current method of 1,000 Hz after standing for 0.5 hour after charging.

Example 15 The copper plating in Example 2 was replaced with the electroless copper bath-2,
The above copper cyanide bath: b-3) was used, and the same rotating and tilting barrel plating apparatus as in Example 14 was used.
Copper plating was performed under the conditions of 5 A / dm ² and a plating time of about 5 minutes to obtain a nickel powder whose almost entire surface was covered with a copper film having an average thickness of about 1 μm. Next, silver plating was performed under the same conditions as 1) of Example 14 to obtain a nickel powder: Ag / Cu // Ni whose almost entire surface was covered with a silver / copper double film.

A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in Example 14-3) except that the obtained nickel powder coated with a silver / copper double film was used. 1
A nickel-metal hydride battery was fabricated by combining the positive electrode of 4), the separator of 4) of Example 1 and the alkaline electrolyte of 5), and prepared under the same conditions as 4) of Example 14).
A zero cycle life test was performed. Table 2 shows the test results.

Example 16 In Example 14-1), an electroless silver bath: a-2) was used in place of the silver cyanide bath as the plating bath, and nickel powder coated almost entirely with a silver-only film was used. : Ag // Ni was obtained. A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in Example 14-3) except that the obtained nickel powder coated nickel powder was used, and a positive electrode of Example 14-2) was obtained. A nickel-metal hydride battery was fabricated by combining with the separator 4) of Example 1 and the alkaline electrolyte of 5), and a 1,000 cycle life test was performed under the same conditions as 4) of Example 14). Table 2 shows the test results.

Example 17 In Example 15, the above nickel sulfamic acid bath: c-1) was used in place of the silver cyanide bath, and the bath temperature was 30.
Temperature, pH: 3-4, average current density: 2 A / dm ² , nickel plating on the copper film, and nickel / copper / nickel powder coated on almost all surfaces with a nickel / copper double film: Ni / Cu /
/ Ni. A hydrogen storage alloy electrode (negative electrode) was prepared by the same treatment as in Example 14-3) except that the obtained nickel / copper double film-coated nickel powder was used. A nickel-metal hydride battery was prepared by combining the positive electrode of (1), the separator of (4) of Example 1, and the alkaline electrolyte of (5), and subjected to a 1,000 cycle life test under the same conditions as in (4) of Example 14). Carried out. Table 2 shows the test results.

Example 18 In Example 1-1), a three-dimensional chain structure having a bulk density of 0.3 g / cc and a specific surface area of 2 m ² / g, which was treated with alkali under the same conditions in place of nickel powder, was used. Carbonyl nickel powder, electroless silver bath-1: a-1)
The procedure was the same except that an electroless silver bath-2: a-2) was used in place of the above, to obtain a carbonyl nickel powder: Ag // NiC whose almost all surface was coated with a silver-only film of about 0.1 μm. Was.

Example 14 except that the obtained carbonyl nickel powder coated with the silver-only film was used as a conductive agent.
A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in 3) above, and nickel was combined with the positive electrode of Example 14-2), the separator of Example 1-4) and the alkaline electrolyte of 5). A hydrogen battery was manufactured, and a 1,000 cycle life test was performed under the same conditions as 4) of Example 14). Table 2 shows the test results.

Example 19 The procedure of Example 18 was repeated, except that untreated carbonyl nickel powder was used.
Carbon / nickel powder: Ag // NiC whose almost all surface was covered with a 1 μm silver single film was obtained.

Example 14 except that the obtained carbonyl nickel powder coated with the silver-only film was used as a conductive agent.
A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in 3) above, and nickel was combined with the positive electrode of Example 14-2), the separator of Example 1-4) and the alkaline electrolyte of 5). A hydrogen battery was manufactured, and a 1,000 cycle life test was performed under the same conditions as 4) of Example 14). Table 2 shows the test results.

Example 20 In Example 18, the plating bath was changed to the above-mentioned silver sulfate bath: a-5)
Alkali-treated carbonyl nickel powder coated almost entirely with a silver-only film using a rotary inclined barrel plating apparatus, silver plating under the conditions of an average current density of 0.2 A / dm ² and a plating time of 48 seconds. : Ag // NiC was obtained.

Example 14 except that the obtained carbonyl nickel powder coated with the silver-only film was used as a conductive agent.
A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in 3) above, and nickel was combined with the positive electrode of Example 14-2), the separator of Example 1-4) and the alkaline electrolyte of 5). A hydrogen battery was manufactured, and a 1,000 cycle life test was performed under the same conditions as 4) of Example 14). Table 2 shows the test results.

Example 21 In Example 18, the plating bath was replaced with the above electroless copper bath-2: b
-2), copper plating is performed for about 0.7 minutes under the conditions of pH: 12 to 13, temperature: 60 ° C., deposition rate: 8 to 10 μm / h, and almost the entire surface is made of a copper-only film having an average thickness of 1 μm. Coated alkali-treated carbonyl nickel powder Cu //
NiC was obtained.

Example 14 was repeated except that the obtained carbonyl nickel powder coated with the copper-only film was used as a conductive agent.
A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in 3) above, and nickel was combined with the positive electrode of Example 14-2), the separator of Example 1-4) and the alkaline electrolyte of 5). A hydrogen battery was manufactured, and a 1,000 cycle life test was performed under the same conditions as 4) of Example 14). Table 2 shows the test results.

Example 22 In Example 18, the plating bath was replaced with the above electroless copper bath-2: b
-2), copper plating was performed for about 0.46 minutes under the conditions of pH: 12 to 13, temperature: 60 ° C., and deposition rate: 8 to 10 μm / h, and a copper-only film having an average thickness of 0.07 μm was almost entirely formed. An alkali-treated carbonyl nickel powder coated on the surface was obtained. Subsequently, silver plating was performed under the same conditions as in Example 20, and a carbon / nickel powder coated with a silver / copper double film further covering the copper film with a silver film having an average thickness of 0.03 μm:
Ag / Cu // NiC was obtained.

The hydrogen storage alloy electrode (negative electrode) was treated in the same manner as in Example 14-3) except that the obtained carbonyl nickel powder coated with the silver / copper double film was used as a conductive agent.
Then, a nickel-hydrogen battery was prepared by combining the positive electrode of Example 14-2), the separator of Example 1 4) and the alkaline electrolyte of 5).
A 1,000 cycle life test was performed under the same conditions as in the above. Table 2 shows the test results.

Example 23 In Example 18, the plating bath was replaced with the above electroless silver bath-1: a
−3) to obtain an alkali-treated carbonyl nickel powder: Ag // NiC, which is almost entirely covered with a silver-only film having an average thickness of 0.01 μm. A hydrogen storage alloy electrode (negative electrode) was prepared in the same manner as in Example 14-3), except that the obtained carbonyl nickel powder coated with the silver-only film was used as a conductive agent. A nickel-metal hydride battery was manufactured by combining the positive electrode of 2), the separator of 4) of Example 1, and the alkaline electrolyte of 5), and was subjected to 1,000 cycles life under the same conditions as 4) of Example 14). The test was performed. Table 2 shows the test results.

Example 24 In Example 23, the average thickness of the silver-only film was 0.5 μm.
A nickel-metal hydride battery was fabricated in the same manner as in Example 23, except that
A 000 cycle life test was performed. Table 2 shows the test results.

Comparative Example 2 In Example 23, the average thickness of the silver-only film was 0.001.
except that the thickness of the nickel
A hydrogen battery was fabricated and subjected to a 1,000 cycle life test under the same conditions as in 4) of Example 14). Table 2 shows the test results.

Comparative Example 3 A hydrogen storage alloy electrode (negative electrode) produced by the same method as in Example 1-3) was used instead of the hydrogen storage alloy electrode (negative electrode) used in Example 15-4). Then, a nickel-metal hydride battery was produced in the same manner as in Example 23, and a 1,000 cycle life test was performed under the same conditions as in 4) of Example 14). Table 2 shows the test results.

[0056]

[Table 2]

In a positive electrode using γ-nickel oxyhydroxide as an active material, a current distribution is made uniform and an electrode reaction is made uniform by interposing a conductive agent coated with a silver single film or a silver / copper double film. I do. As a result, as shown in Table 1, while the discharge capacity is improved, the drop of the highly available γ-nickel oxyhydroxide is suppressed even when the quick charge is performed,
It shows a high discharge capacity retention rate over a long period. On the other hand, also in the hydrogen storage alloy electrode, the current distribution in the electrode is made uniform by interposing a conductive agent coated with a film mainly composed of silver or copper having a small electric resistance. As a result, as shown in Table 2, a high discharge capacity and a high retention rate are obtained, and the internal pressure and internal resistance of the battery are reduced. In particular, in a system using carbonyl nickel powder having a three-dimensional chain structure as the conductive agent, a higher discharge capacity and lower internal resistance can be obtained.

[0058]

Industrial Applicability The present invention provides a positive electrode and a hydrogen storage alloy electrode (negative electrode) having a discharge capacity, a high discharge capacity retention rate, excellent cycle life characteristics, and suitable for use in an alkaline secondary battery having a low internal pressure and a low internal resistance. ), And its industrial significance is extremely large.

[Brief description of the drawings]

FIG. 1 is a schematic view of an internal anode rotary inclined barrel plating apparatus used in an embodiment.

Claims (1)

[Claims] 1. An electrode for an alkaline secondary battery, comprising an active material and a conductive agent powder having a coating essentially consisting of silver, copper, or both on at least part of the surface.